COMPUTERIZED CEPHALOMETRIC EVALUATION OF ORTHOGNATHIC SURGICAL PRECISION AND STABILITY IN RELATION TO MAXILLARY SUPERIOR REPOSITIONING COMBINED WITH MANDIBULAR ADVANCEMENT OR SETBACK

Purpose: A computerized, cephalometric, orthognathic surgical program (TIOPS) was applied in orthognathic surgical simulation, treatment pla nning, and postoperatively to assess precision and stability of bimaxi llary orthognathic surgery. Patients and Methods: Forty consecutive pa tients with dentofacial deformities requiring bimaxillary orthognathic surgery with maxillary superior repositioning combined with mandibula r advancement or setback were included. All patients were managed with rigid internal fixation (RIF) of the maxilla and mandible and without maxillomandibular fixation (MMF). Preoperative cephalograms were anal yzed and treatment plans produced by computerized surgical simulation. Planned, 5-week postoperative and 1-year postoperative maxillary and mandibular cephalometric positions were compared. Results: In the mand ibular advancement group, the anterior maxilla was placed too far supe riorly, with an inaccuracy of 0.4 mm. The posterior maxilla and the an terior mandible were placed in the planned positions. The lower poster ior part of the mandibular ramus was placed too far anteriorly, with a n inaccuracy of 2.0 mm. However, the mandibular condyles were accurate ly placed. In the setback group, the anterior maxilla was placed too f ar superiorly and posteriorly, with a vertical and sagittal inaccuracy of 1.0 mm and 0.7 mm, respectively. The posterior part of the maxilla was placed in a posterior position with an inaccuracy of 1.9 mm. The anterior mandible was placed too far anteriorly with an inaccuracy of 0.9 mm. The lower posterior part of the mandibular ramus was placed in a posterior position with an inaccuracy of 0.9 mm. However, the mandi bular condyles were accurately placed. The statistical analysis of the 1-year stability data showed that the maxilla had moved 0.3 mm poster iorly in the advancement group and the lower incisors had moved 0.8 mm superiorly. No other significant positional maxillary or mandibular c hanges were found. In the setback group, the maxilla had moved 0.5 mm posteriorly, the anterior mandible 0.5 mm anteriorly, and the lower in cisors 0.7 mm superiorly. No significant positional changes were seen in the mandibular ramus. Conclusion: The TIOPS computerized, cephalome tric, orthognathic program is useful in orthognathic surgical simulati on, planning, and prediction, and in postoperative evaluation of surgi cal precision and stability. The simulated treatment plan can be trans ferred to model surgery and finally to the orthognathic surgical proce dures. The results show that this technique yields acceptable postoper ative precision and stability.